Oil-free compartment for transformer tank for mounting low voltage bushing



1965 M. BROVERMAN ETAL 3,164,794

OIL-F REE COMPARTMENT FOR TRANSFORMER TANK FOR MOUNTING LOW VOLTAGE BUSHING Filed Nov. 29, 1962 United States Patent 3,164,794 OIL-FREE CQMPARTMENT FOR TRANS- FQRMER TANK FOR MOUNTING LOW VBLTAGE BUSHKNG Itl'ichael Eroverman and Francis L. Woods, Pittsiicld,

Mass, assignors to General Electric Company, a corporation of New York Filed Nov. 29, 1962, Ser. No. 240,953 5 Claims. (Cl. 356--92) This invention relates to stationary electromagnetic induction devices, and more particularly, to electromagnetic induction devices, such as transformers and the like, having a lower, oil-free compartment for the mounting of low voltage bushings.

As is well known to those skilled in the art, many types of electromagnetic induction devices, such as transformers and the like, are enclosed in a metal tank and are provided with a liquid dielectric for providing insulating means to the transformer components within the metallic tank. In many of these devices, particularly the transformer type devices which are designed to be mounted on poles, the transformer is provided with high voltage bushings and low voltage bushings which are, in general, mounted on either the cover of the tank or on the upper wall of the tank. it is generally the fashion in pole type transformers, for example, to mount both of the bushings either on the cover of the tank or on the upper wall at a position which is well above the level of the liquid dielectric contained within the transformer tank. As an example, see Patent No. 2,937,253 which shows both the hi h voltage bushings and the low voltage bushings mounted on the side wall of the transformer tank well above the level of the liquid dielectric within the tank. In some instances the low voltage bushings have been mounted at or below the level of the liquid dielectric within the tank, and in such cases it is required that an oil-type seal be provided between the bushing and the wall in order to prevent leakage of the liquid dielectric. An example of such oil-type seal is shown in Patent No. 2,827,320.

As is well understood by those skilled in the art, when various types electromagnetic induction devices, such as transformers and the like, are mounted on poles and where the top mounted bushings are provided, it is required that the lineman work on such bushings in the vicinity of the high voltage lead which extends to the transformer or similar electromagnetic induction device. Obviously, working on low voltage bushings in close proximity to high voltage leads could create a danger to the lineman which all manufacturers and utilities desire to eliminate, where possible. Further, as is well known where the bushings are provided on the top portion of the tank, it is often necessary to provide a secondary rack on the pole, whereby the secondary leads may be connected from the bushings to the rack and thence taken from the rack to the service entrances of the various consumers who are to be served by the electromagnetic induction device mounted on the pole.

It has long been considered desirable to mount the low voltage bushing on the bottom wall of the transformer tank. In tins position the low voltage bushings would be more accessible to the lineman while working on the pole, and it would also eliminate the dangers present for the lineman working in close proximity to the high voltage lead which extends to the polemounted, electromagnetic induction device. Further, as will be understood, by providing the low voltage bushings 0n the lower portion of the tank it would also be possible, in many instances, to eliminate the need for secondary racks on the pole. With such mounting it would be possible to carry the service leads directly from the secondary bushings to the service entrance of the consumers to be serviced by the pole-mounted, electromagnetic induction device. However, one of the principal objections to be found in using low voltage bushings on the lower end of the transformer tank is the problem involved in leakage of oil, which is always present, especially where the bushings are subject to breakage, for example, by the dropping of tools onto the bushings or by pranksters who have a tendency to utilize the bushings as targets for rocks and rifle fire. As is well understood, where such bushings are broken and where they are below the level of the liquid dielectric in the tank the liquid dielectric tends to leak out of the broken bushings; leading to costly repairs of the tank in that it must be removed from the pole in order to replace the bushing and refill the tank with liquid dielectric. Also, as will be understood, if the leakage of liquid dielectric is severe and is not discovered at an early time, it is possible to destroy the transformer due to operation of the transformer without the required liquid dielectric in the tank. Thus, it is seen, that there is a great need at this moment in the art for a pole-mounted electromagnetic induction device in which low voltage bushings may be provided on the lower tank wall, and which will not be subjected to the problem of leakage of the liquid dielectric if such bushing should become accidentally broken.

It is, therefore, a principal object of this invention to provide an electromagnetic induction device with low voltage bushings mounted on the bottom wall of the tank of the induction device, which bushings are free from the dielectric liquid in the tank.

A further object of this invention is to provide an electromagnetic induction device having a compartment for the mounting of low voltage bushings, which compartment is free from the liquid dielectric in the electromag netic induction device tank.

A still further object of this invention is to provide a transformer tank having low voltage bushings extending from the lower portion of the tank and in which secondary leads are carried to the low voltage bushings through a substantially liquid dielectric-free passage.

In carrying out this invention in one form, an electromagnetic induction device is provided with a tank having an extending wall below the sealed base of the tank. A standpipe is provided, extending from the base to a point above the level of the liquid dielectric material within the tank. An opening is provided in the sealed base within the standpipe through which the secondary leads may.

extend to secondary bushings which are mounted on the lower extended tank wall. In this manner, low voltage bushings are provided which are completely free of the liquid dielectric material within the electromagnetic induction tank.

The invention which it is desired to protect will be clearly pointed out and distinctly claimed in the claims appended hereto. However, it is believed that this invention will be better understood, and the manner in which 3 its various objects and advantages are obtained, as well as other objects and advantages thereof, by consideration of the following detailed description of a preferred embodiment thereof, especially when considered in the light of the accompanying drawing in which:

FIGURE 1 is a perspective view of a pole-mounted transformer being provided with bottom mounted low voltage bushings according to this invention;

FIGURE 2 is an enlarged sectional view of a transformer, as shown in FIG. 1, showing a preferred form of this invention; and

FIGURE 3 is a partial sectional view showing a modified form of the invention.

Referring now to the drawings, and especially to FIG. 1 thereof, an induction device 1%, for example, a transformer, is shown in perspective view. The transformer 10 comprises a tank 12 and a cover 14. The transformer 10 is mounted on a pole 16 in a manner which will be well understood by those skilled in this art. The transformer it) is provided with at least one high voltage bushing 18 on the upper portion of the tank wall 12, and is further provided with a plurality of low voltage bushings 20 which are mounted on the lower portion of the tank wall 12. By means of this manner of mounting the low voltage bushings, the lineman can readily work on the low voltage bushings 24) without being in close proximity to the high voltage lead 22 which is secured to the high voltage bushing 18, in a manner well understood by those skilled in this art. Also, in many instances, it will be possible to eliminate the need for a secondary rack on the pole since the secondary leads may be taken directly from secondary bushings 24) to the service entrance of the consumer to be serviced by the induction device it). In order to provide the low voltage bushing mounting on the lower portion of the tank wall 12 a novel tank construction is provided, which is shown in a preferred form in FIG. 2 of the drawing.

Referring now to FIG. 2 of the drawing, the electromagnetic induction device is shown as a transformer 10 having a core and coil unit 24 which is mounted within the tank 12. The core and coil unit 24 are mounted on a sealed base 26 which is firmly secured to the side Wall of the tank 12, in any desired manner, such as for example, by welding. A transformer cover 14 is also provided, the transformer cover 14 being sealed to the tank 12 in any desired manner. In the usual manner, a liquid dielectric material 28, such as for example, electrical grade transformer oil or a halogenated hydrocarbon liquid dielectric material, is provided within the tank 12 completely surrounding and covering the core and coil unit 24. A primary lead or high voltage lead (not shown) is brought into the tank from bushing 18 (not shown in FIG. 2) and is connected to the core and coil unit 24 in a manner well understood by those skilled in this art.

A plurality of secondary leads, only secondary lead 3%) being shown, are brought from the core and coil unit 24 to a secondary lead rack 32 mounted on the core and coil unit 24. A standpipe 34 is provided within the tank 12 and is firmly secured to the base 26, in any desired manner, such as for example, by welding. An opening 36 is provided in the base 26 within the standpipe 34, as shown. The walls of the tank 12 extend below the sealed base 26, as is indicated at 38 in the drawing. The low voltage bushings 20 are mounted on the extending portion 33 of tank wall in any desired manner so as to be firmly secured to the tank extension 38. The secondary leads from the transformer rack 32 are carried out through standpipe 34 and are connected to bushing 29 in the manner shown by secondary lead 46 in the drawing. As will be understood it is normal to provide three secondary leads from the core and coil unit 24 to the low voltage bushing 20; however, only one is shown so as to simplify the drawings utilized herein.

If desired, a sealing means may be provided in the opening in the top of standpipe 34 and about the secondary lead td, in the manner indicated by the sealing member 42. Sealing member 42 will prevent any contaminants from ent ring through the standpipe 34 and into the liquid dielectric material 28. Further, in the unlikely event that the liquid dielectric material should be splashed above the level of the standpipe 34- the sealing member 42 will prevent such dielectric material from leaking out through standpipe 34.

While a single sealed base member 26 is sufficient for the transformer it), in many instances it is desired to provide a second base member 4 on the lower end of the tank extension 38 in order to provide protection for the inside of bushing 29 and the secondary lead 44) extending along the bottom of the main base 26 of the transformer. The second base member 44 may be welded to the lower end of the tank extension 38, if desired, in a fluid tight manner to prevent contaminants from entering the compartment 46 which is formed between main base member 2-5, the second base member 44, and wall extensions 38.

As is well known, in some transformer designs it is necessary to establish the height of air space above the liquid dielectric so that in operation a predetermined pressure will not be exceeded. This pressure is established by the temperature within the transformer and by the expansion of the liquid dielectric within the transformer tank. It is possible to provide such designs, utilizing the low voltage bushing mounting of this invention, without increasing the height of the transformer. One form of construction which may be used is shown in FIGURE 3 of the drawing. As is shown in FIGURE 3, the top of standpipe 34 is provided with a flared member 42 instead of the liquid seal means 42. Member 42 allows free interchange of air between the lower chamber 46 and the top portion or chamber 48 of the tank above the oil. By use of member 42' the top chamber and lower chamber 4. 6 are effectively in series, providing the desired air space above the dielectric liquid. Of course, it will be understood that in this construction the second base member 44 (FIGURE 2) will be welded to the tank extension 38 in a fluid tight manner, as earlier explained.

It is desired that member 42 be provided, in the form of a flared collar, as shown in FIGURE 3, to prevent any liquid dielectric, which might be splashed during movement of the transformer from entering the standpipe 34. Obviously, the collar 42 could be omitted, if desired, without interferring with the series operation of the chambers 46 and 48.

While there has been shown and described the present preferred embodiment of forming the oil-free, low voltage bushing of this invention, it will be understood that many changes may be made .in the construction of the various components of the tank assembly, if desired, without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed as new and which it is desired to secure by Letters Patent of the United States is:

1. A transformer for mounting on a pole, comprising; a transformer tank having a wall, a cover member and a sealed base member, the wall of said tank extending below said sealed base member, a core and coil unit mounted in said tank on said sealed base member, a liquid ielectric in said tank completely covering said core and coil unit, a standpipe secured in a fluid-tight manner to said base within said tank, said standpipe extending from said base to point above the level of said liquid dielectric, and opening in said base Within said standpipe, a bushing mounted on said extended wall of said tank and a secondary lead extending from said core and coil unit through said standpipe to said bushing.

2. A transformer as claimed in claim 1 in which a liquid-tight seal is mounted on said standpipe, surrounding said secondary lead.

3. A transformer as claimed in claim 1 in which a sec- 0nd sealed base member is provided below said extended References Cited by the Examiner wall to seal out dirt and dust and to protect the internal UNITED STATES PATENTS portion of said bushing.

4. A transformer .as claimed in claim 3 in which a flared 2668274 2/54 Schnelder 336-407 X collar member is provided on top of said standpipe to 5 FOREIGN PATENTS ptrevgnt said liquid dielectric from splashmg into said 368247 2/39 Italy. 8 an PIPe' 473,126 7/52 Italy.

5. A transformer as claimed in claim 3 in which a fluid-tight seal is mounted on said standpipe, surrounding JOHN F BURNS Primary Examiner said secondary lead. 10 

1. A TRANSFORMER FOR MOUTING ON A POLE, COMPRISING; A TRANSFORMER TANK HAVING A WALL, A COVER MEMBER AND A SEALED BASE MEMBER, THE WALL OF SAID TANK EXTENDING BELOW SAID SEALED BASE MEMBER, A CORE AN COIL UNIT MOUNTED IN SAID TANK ON SAID SEALED BASE MEMBER, A LIQUID DIELECTRIC IN SAID TANK COMPLETELY COVERING SAID CORE AND COIL UNIT, A STANDPIPE SECURED IN A FLUID-TIGHT MANNER TO SAID BASE WITHIN SAID TANK, SAID STANDPIPE EXTENDING FROM SAID BASE TO POINT ABOVE THE LEVEL OF SAID LIQUID DIELECTRIC, AND OPENING IN SAID BAE WITHIN SAID STANDPIPE, A BUSHING MOUNTED ON SAID EXTENDED WALL OF SAID TANK AND A SECONDARY LEAD EXTENDING FROM SAID CORE AND COIL UNIT THROUGH SAID STANDPIPE TO SAID BUSHING. 